Wireless telegraphy.



*01. M.l GREEN'. Y WIRELESS TBLEGRAPH.

APP-I IQATION' FwILED SEIPTLBO, 1907.

Patented June 27,1911.-

f lli mgm-55m 3. uw uw 'UNiTED sTATEs PATENT OFFICE.

, CHARLES M'. GREEN, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRI COMPANY, A CORPORATION 0F NEW YORK.

WIRELESS TELEGRAPHY.

Specification of Letters Patent. Patented J une, 27, A1911.

' Appueation'mea september 30,1907. serai No. 395,094.

, 10 wireless or space Vtelegraphy, and it comprises a system of multiplex wireless teleg,

raphy in which multiphase` currents are employed for the charging of the condensers, by the discharge of which electromagnetic waves are started at an elevatedconductor or antenna, which waves propagate through space and are absorbed at a dlstant station or stat-ions by another elevated conductor or conductors, and there actuate selectively certainresponsive devices for the production ot' signals.

The idea which underlies my invention 1s based npon the consideration that at a wireless telegraph transmitting station the electromagnetic waves by which messages are transmitted emanate from the antennae only during the time of the rapidly diminishing, oscillating condenser discharges, which tnne is only a very small'4 fraction of the duration of a half cycle yof the 4alternating current which charges the condenser. If, therefore, a multiph-ase current is employed for charging a'number of condensers, each phase may be diverted to and confined to a different charging each condenser may be controlled by independent transmitting keys and suitably timed conjugating or selector devices, whereby it becomes practicable to send as many independent messages from the same station as there are multiphase currents elnployed for the charging of the condensers,. In a system. of this character it is necessary .to make certain that a phase of current which charges one condenser shall not, at tl'ife'v'same time, charge any of the other condensers, and this selective. joining of each current-phase with a distinct condenser is, in accordance'with my invention, e ffected by certain devices which may be called selectors or conjugators. If, in a system of this character, two-phase currents are employed,` the system will be a duplex telegraph; if a three-phase current is employed, the system becomes a triplex telegraph; and.,generally,

condenser, and the time of charging and distem becomes a multiplex telegraph.

In the accompanying drawing, which forms a part of this specication, I have illustrated in diagram an apparatus which may be used in the practiceof my invention as applied to a triplex system of wireless telegraphy, but it will be obvious to those skilled in Ithe art that the invention is applicable to the use of currents of any numberv of phases.

In this drawing, a three-phase system of electrical supply, represented by the conductors L1, L2, L3, 1s tapped by the three transmitting circuits A, B, C, each cont-aining the primary p of a step-up transformer,

'a non-'inductive resistance nin series with the primary of the transformer, and a transmitting rkey le, shunting the resistance. The s'econdaries s of the transformers are each in a circuit that includes two i'nd'uctances z', e', two selector devices or conjugators S., Sa, or Sb S5, or Sc Se, and one of the condensers Ca, Cb, Cc, respectively, all in series. One armature of each condenser is connected with the like armature ofthe othercondensers by `the conductor d, and the other armatures of the condensers are connected each through a selector Sa, Sb, Sc, respectively, with a reactance coil I. One end of this reactance coil is connected by a conductor e with the ground at G, and at the other end with the elevated'condu'ctor E. In addition to this, the common terminal of one armature of the condensers, the conductor d, is also connected to ground by a conductor'Y f anda general selector or conjugator Sg.

Each conjugator consists of a rotating element g and two stationary elements t. Except in the case of the conjugator Sg, the rotating element is a simple two-armed blade, rotating about an axis passing through its middle. In the case of the conjugator, Sg, the rotating element Vconsists of three intersecting blades having their 'common axisfof rotation at the point of intersection, as indiif ln-phase currents are employed, the syscated; it has, therefore, six arms projecting cally opposite each other, so that the rotary element will sweep past but close the sta- Irant of a circle; they are placed diametritionary elements .during one half of each revolution. In the case of the other donjugators, the stationary elements 'have no appreciable width, .but are reducedv to a simple wire terminal 'or the edge of a strip of metaLfacing the edge, ofthe rotating element. In all these selectors or conjugators the rotary element sweeps past the stationary elements so close that for theihigh potential charges or discharges which"Ik pass through these conjugators the circuits in which they are-included are practically closed at the times when the rotary and stationary elements are in opposition."

Differentpoints of the inductancecoilI are connected each to one of the stationary Y elements of the conjugators Sa, Sb, Sc, by

the conductors u,.and the points of connection at the inductance coilg are selected in a manner which will be pointed out farther on. The inductance coil lI ispreferably constructed without magneticcore, because this coil, ora ortion thereof, forms a part of a number o .sonorous circuits, as will appear farther on, and the accurate tuning of such circuits in accordance with certain well known rules, is more reliable when no ironp or other .magnetic material is employed.

` The rotors of the selectors or conjugators are all driven in synchronism with the periodicity of the multiphase current employed, and those belonging Atothe same' transmitting station are displaced in space' with reference to those belonging to another transmitting station by an angle corresponding to the time difference between the phases of the multiphase current employed. In the example illustrated in the drawing, where a three-phase current is employed, the rotors rotors may be effected in any desirable way,

but is most accurately secured by suitably gearing the rotors to the rotor of the multiphase current generator. Actual physical contact between the rotors and stators of the selectors Sa, Sb, Cc, is preferably avoided, since I have found that with the employment Yof sufficiently high voltages such Acontact is not necessary, and the irregularitiesand the wear 'and tear due to ph sical contact are thereby avoided; but whi e this is the construction and mode of operation which I prefer, and While this isy a feature of my invention,I am by no means restricted thereto,

since it is practicable to'make actual brushcontact between'these rotors and stators.

In the caselof the selectors Sa, Sb, Sc,

Vmomentary condition of the apparatusrepresented inthe drawing, the secondary circuit of the step-up transformer for station A- is open at the selectors Sa, Sa, while the circuit from the condenser Ca at that station, to the inductance coil I is closed at the se -lector Sa. Similarly, the'secondary circuit of the step-up transformer for station B, is

'closed at the selectors Sb, Sb, while the .cir-

cuit from the condenser at Cb at that station, to the inductance coil I, is open at the selectorfSb. For station C the conditions of thecircuits are the same as for stationB, andthe general selector Sg, in the condition .shown in the drawing, closes. the ground connection from the common condenser terminal d by conductor f.

The mode of operation of the system, so far described, is readily understood. Let it be assumedthat the rotors of the selectors are"drivenclockwise and that three-phase current is established in the lines L1, L2, L3. In-that case, in the momentary 'conditionof the apparatus shown in the drawing, the primary circuits takeeach one phase of current, but the secondary circuit of station A being open, its condenser C,l receives no charge; but under the supposition that it has beencharged at an earlier stage -of the operation, it will now"discharge in the circuit which includes the selector Sa, conductor u, that portion of the inductance coil which is `interposed between conductor u and the general selector, the general selectoi` itself, and the conductors f and ci. Each discharge determines a great difference of potential between the antenna andthe earth, and the emission of electromagnetic waves from the antenna. The discharges are oscillatingy ones, the periodicity of which depends upon the capacityof the condenser andthe inductance of the portion of the inductance coil in this circuit. The periodicity isdetermined in accordance with the well known expression wherein T is the duration of the period, C the localized capacity, and L the localized inductance of the circuit. The frequency,

. T 4 of the oscillating discharges can thus be ISO above formula. i

predetermined and is usually made rather great, several millions per second. By assigning to the lthi'ee discharging circuits largely different frequencies, the frequencies and lengths ofthe electro-magnetic waves due to the operation of the three stations become correspondingly different, and may, therefore, be selectively absorbed by .three distinct receiving circuits, which are tuned respectively in unison with the three discharging circuits. in accordance with the The condenserscan only be charged while the rotors of selectors Sa, Sb, Se, respectiiv'ely, are in virtua'l or actual contact with their -stators, and the condensers can lonly dis- .i charge when the rotors of the selectors Sa,

Sb, Sc, respectively, are in virtual contact withitheir stators; provided 'that at such times the discharging circuit is closed at the general selector Sg. This is the reason cable 4to keep the discharging circuit at this point permanently closed, as, by a wire z, and switch t; but I prefer to use this general selector, whereby the condensers are cut off from the ground, exceptat the moment of discharge.

` The resistances r, 0, r, in the primary .transmitting circuits are so large that these circuits take exceedingly little current so long as the keys'. are in the open position `shown inthe drawing, so that at such times the stations do practically no work, and

the y energy of the electromagnetic waves emanated by the antenna is so small that a e ydistant receiver; is not thereby. actuated.

pliaseonly of the multiphase current, to the exclusion of the other phases, and since the When, however, t a` key is-depressed, and

thereby the resistance shunted, the correspendingprimary circuit takes a large current and the station emits practically effectivesignals in accordance with the code employed.

Since each transmitter has control of one oscillating `,discharges ultimately produced byany transmitter have widely different,

frequencies from those produced by the other transmitters, it is clear that all the'transmittersy may work simultaneously without interference or merging ofthe signals; each operator can therefore work without regard to the others, and two, three 'or Vmore independent messages may thus be transmitted simultaneously. Each message 4or signal is characterized by short groups of .electromagnetic waves of a distinct and predetermined frequency. -How these independent messages or signals can be selectively received at distant stations is well known to rent 'need not be high, since withI such low periodicity as 25 per second,.each transmitter has control ofthe current twenty-five Vtimes per second, each time for 1 `of a second. This is ordinarily sufficient; but a much higher frequency may comfortably be employed.

In the use of this process by Ameans f the apparatus described,.the terminals of the rotors and stators of the discharging selec-l tors,'and Vthe air gaps between them at the times of opposition, take the place of the ordinary air gap or discharging devices, and these terminals will, therefore, be made vof a material suitable for this purpose. The

same thing is true of the general selector, if such beused. The division of the air gap tends to prolong the useful life of these devices, vand has other advantages. Y

I/Vhile I have shown two inductance and two'charging selectors for each transmitter,

one only may be used if so desired, but it is preferable to use two, one in each side of the secondary circuit. l

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of simultaneously transmitting two or more distinct wireless signals, which consists in causing the emission of twoor more trains of electromagnetic waves of diHerent-periodicities in multiphase' current time relation, and breaking each trainindependently into groups in accordance with a code.

2. The method *of simultaneously transmit-ting two.or more distinct wireless signals from a common antenna, which consists in impressing upon the latter two or more trains of electric potentials of different periodicities in `multiphase current` time relation, and breaking each train independently into groups in accordance with'a code.

' 3. Thev method of transmitting wireless signals, which consists in establishing and maintaining the emission of periodic electromagnetic waves of ineffective volume, and reinforcing said waves in accordanc with the desired signals.

4. The method of simultaneously transmitting two Vor more distinct wireless sighals, which consists in establishing andl -maintaining the emissio-n of two or more trains of electromagnetic waves in multiphase current time relation, 'each of a different frequency and all of ineffective voliio urne, and independently reinforcing two or more of the trains, each in 'accordance' with the desired signal.

5.. The method of simultaneously transmitting two or more distinct wireless signals from the same antenna, which consists in charging two or more condensers selectively each vby a different phase of a multiphase current and in code accordance with a different signal, discharging the different condensers each at a different frequency in 7. A multiplex wireless telegraph trans: I nitter, comprising an antenna and meansA forimpressing upon the latter two or more trains of electric potentials of. different periodicities in mult-ipha'se current time relation,-

and means for breaking` each train indel pendently into groupsl in accordance with a code. A

' 8. A wireless telegraph transmitter, comprising means for establishing and maintaining periodic electromagnetic waves of ineffective volume, and means fory reinforceriodicities in ing said waves in accordance with;` the desired signals. y'

9. Av multiplexwireless telegraph transmitter, comprising means for establishing and maintaining two or-more vtrains of electromagnetic waves in mult-iphase `current time relation, each` of adifferent frequency and all of ineffective volume,'andv meansffor independently reinforcing two or more of the trains, each in accordance with a desired p signal. l Y

10. A multiplexf'wireless 4telegraph trans- .mitter station, comprising an antennatwo or more condensers, means for charginge'ach condenser by a diiferent phaseof'a multiphase current and each during -code intervals corresponding to a diferent'mes's'age, a

di'erentlytuned resonant discharging circuit for each condenser, and an antenna and ground connection l common to all,v con'denrsers. y v v l i In witness whereof, 'I have hereunto set my hand this 26th`dayf0f September, '1907.

CHARLES M, GREEN.

Witnesses:

JOHN A. McMANUs, J r., ROBERT SHAND. l

Copies of this patent may be obtained for ve cents each, byfadiressing the Commissioner of Patents,l

' Washington, D. C. 

